Radio transformer



1932- I H. J. ROUND 1,869,914

RADIO TRANSFORMER Original Filed March 31 1920 rfw w rl l l l l l l i WAVE lib 6 7' h INVENTOR HENRY JOSEPH ROUND A ORNEY coupled by means of atransformer formed Patented Aug. 2, I932 UNITED STATES PATENT OFFICE-HENBY JOSEPH ROUND, OF MUSWELL HILL, LONDON, ENGLAND, ASSIGNOB, TO RADIOCORPORATION OF AMERICA, A.

conronarrouor DELAWARE name rnmsronunn Original application filed larch81, 1920, Serial No. 370,175, and in Great Britain Kay 13, 1819. Dividedand this application filed August 21, 1928. Serial No. 301,088.

This application is a division of my copending application, Serial No.370,17 5, filed March 31, 1920 for thermionic receiving devices forwireless telegraphy and telephony.

This invention relates to improvements in thermionic receivin devicesfor wireless telegraphy and telep on and has for its object an'increasedmagni cation of signals.

According to this invention two valves are of resistance wire with anair core herein after called a resistance transformer and so arrangedthat the ratio of inductance to capacity is as great as possible. Morethan two valves may be arranged in cascade, each valve being coupled tothe next by a transformer of the kind already described. In some casesthe two windings of a transformer may be connected through a condenser.

The invention is illustrated by the accompanying drawing, Figure 1 ofwhich shows a series of valves in cascade with transformers betweenthem. Figure 2 shows a number of curves illustrating the resultobtained. In Fig. 1 F1, F2, F3 are filaments of three valves which areheated by a common battery B. The grid G1 of the first valve and thefilament F1 are connected to an oscillatory circuit C cou led to anaerial D. The anode A1 of the rst valve is connected to one end of aprimary P1 the other end of which is connected to the positive pole of abatte E in series with the battery B. The secon ary S1 is connected tothe grid G2 and filament F2 of the second valve the anode A2 of which isconnected to one end of a primary P2tl1e other end of which is connectedto the positive pole of the battery E. The secondary S2 is connected tothe grid G3 and filament F3 of the third valve. Each of the transformersP1, S1, P2, S2-is formed of resistance wire with "an air core and thearrangements are such that the ratio of inductance to capacity is asgreat as possible. The two windings of the transformer may be connectedthrough condensers G1, G2 if desired. By increasing the number of valvesand of transformers the magnification of the si nals may. be increasedas desired or uhtil the series begins a self-heterodyne.

The result obtained is illustrated in Figure 2 which shows four curves,the abscissae beingwave lengths and the ordinates Volta es.

The curve 1 shows the voltages obtains at the ends of the secondary ofan air core copper transformer the primary of which is connected to theanode and filament of a valve, such as A1 G1 F1, the transformer havinga natural period which is near the middle of the desired rangeof wavelengths. The curve 2 shows the voltages obtained when the transformerhas such a resistance that the am litude is greatly reduced but at thesame time its maximum occurs at about the middle of the range of wavelengths tolo'e dealt with. It will be seen that this curve is muchflatter than the curve 1, that is, the magnification is considerablyreduced at the resonance point but hardly at all at the limits ofthewave lengths where magnification still occurs.

Gurve 3 shows the voltages that may be obtained by employing a number ofvalves and 7 transformers as shown in Figure 1 while curve 4 shows theefiect when condensers such as C1 C2 are added.

a By. means of this invention it is possible to construct stablecascadeam lifiers having a good range of wave length or waves even as short asmeters.

at I claim is:

1. A transformer adapted to transfer radio freq'uency currents of abroad band of frequencies from the output terminals of an amplifier,comprising a primary winding, a secondary windin inductively coupledthereto, each of said windings being formed of high resistance wire andthe inductance to capacityratio of said windings having such a valuethat the maximum voltage across the terminals of said secondary windinis not substantially greater than twice t e mvoltage as the variousfrequencies of saidmum voltage across the terminals of said secondarywinding at resonance is of the order of one third of the maximum voltageobtained at resonance across the secondary terminals of a similartransformer wound with copper Wire.

3. A transformer adapted to transfer radiofrequency currents of a broadhand of he quencies from the output terminals of an amplifier,comprising a primary winding, a secondary winding inductively coupledthereto, each of said windings being formed of wire of such highresistance that the maximum voltage developed across the terminals ofsaid secondary winding at resonance is less than one-half of the maximumvoltage obtained at resonance across the secondary terminals of asimilar transformer wound with copper wire.

HENRY J. ROUND.

